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009//
Aortic Stenosis
CONTENTS
82
Basics
85
Quantification of Aortic Stenosis
88
Special Circumstances
89
Sub- and Supravalvular Aortic Stenosis
90
Indication for Aortic Stenosis Surgery/Intervention
81
009 // AORTIC STENOSIS
NOTES
Severe asymptomatic aortic
BASICS
Natural History of Aortic Stenosis
stenosis is generally associated
with a favorable prognosis. The
With aortic valve
replacement
Onset of symptoms
100
symptoms occur.
PERCENT SURVIVAL
risk increases dramatically once
Asymptomic stage
75
Without aortic
valve
replacement
50
Heart failure
25
Syncope
Angina
10
Adapted from Ross Circulation 1968
20
YEARS
30
Epidemiology
• 3rd most common form of
heart disease
• Increasing prevalence with older age
(2–6% in the elderly)
• AV sclerosis is a precursor of AS
Hemodynamics in Aortic Stenosis
Patients with aortic stenosis have an increased afterload, which results in LV
pressure overload. Left ventricular hypertrophy is a compensatory mechanism
(reduces wall stress).
Afterload
LV pressure overload
Filling pressure
LVH
Left Ventricular Failure in Aortic Stenosis
Persistent pressure overload leads to deterioration of left
ventricular function and eventually heart failure.
LVF
Low output
Filling pressure
Heart failure
82
009 // AORTIC STENOSIS
BASICS
NOTES
Causes of Aortic Stenosis
In the Western world,
the cause of severe
Congenital abnormalities of the aortic valve are a frequent cause of aortic stenosis.
aortic stenosis in
In some patients a stenosis is present at birth; in others congenital abnormal valves
patients <50 years is
predispose the individual to aortic stenosis later in life (accelerated aging/calcifica-
almost always
tion of the valve).
congenital.
< 70 Years
2%
> 70 Years
2%
2%
3%
23%
18%
50%
48%
27%
25%
Degenerative
Bicuspid
Unicommissural
Postinflammatory
Hypoplastic
Indeterminate
Adapted from Passik et al. Mayo Clinic Proc 1987
Rheumatic Aortic Stenosis
The aortic valve is the
second most common
• Usually mild to moderate stenosis
• May progress to severe aortic stensos
(accelerated valve aging)
• Often combined with aortic
regurgitation
valve involved in
rheumatic heart disease.
• Thickened leaflets/focal calcification
• Often multivalvular disease
Congenital Abnormalities of the Aortic Valve
To establish the diagnosis of a
bicuspid valve, use the short-
• Unicuspid, bicuspid, quadricuspid
• May be associated with genetic
axis view and observe the
• Syndromes (e.g. Down‘s, Heyde‘s)
syndromes (such as Down‘s, Heyde‘s)
opening motion of the valve.
Morphology of the Aortic Valve
A raphe may be small and
subtle. In this setting the
Normal valve (tricuspid)
Functional bicuspid
valve may appear
(tricuspid with raphe) – congenital
tricuspid, especially on a
still frame.
83
009 // AORTIC STENOSIS
NOTES
A dilated ascending aorta
BASICS
Bicuspid – congenital
Unicuspid – congenital
in a young patient may
point to a congenital
aortic valve abnormality.
Echocardiographic Assessment of Aortic Valve
2D
• Valve morphology (cusps)
• Atrial enlargement
• Visual assessment of aortic valve
• Exclude subvalvular membrane
opening and motion
• Degree of calcification
• Left ventricular hypertrophy
• Measurement of the aortic annulus (for
• Left ventricular function
Coronary artery disease is
frequent in calcified
aortic stenosis.
MMode
• Eccentric AV closure
• ”Box” seperation of cusps
TRICUSPID AORTIC VALVE –
zoomed PSAX AV
Calcified aortic valve with reduced opening (aortic valve area=
AVA) in a patient with severe
aortic stenose.
valve sizing in TAVR)
PV
Calcification
Aortic valve area
BICUSPUD AORTIC VALVE –
zoomed PSAX AV
Calcified bicuspid aortic valve
with severe stenosis. Only 2
cusps are visible. It may be
difficult to determine whether a
valve is bicuspid when it is heavily
calcified.
Cusp
84
009 // AORTIC STENOSIS
BASICS
NOTES
Doppler Assessment of the Aortic Valve
Check were aliasing (flow
acceleration) occurs: at
Color Doppler
the valve (valvular AS),
• Color Doppler aliasing caused by high
• Look for the origin of aortic stenosis jet
velocity jet (stenotic turbulences)
below the valve
to exclude LVOT obstruction (SAM/
(subvalvular stenosis)
membrane)?
or above the valve
(supravalvular aortic
CW/PW Doppler
stenosis).
• Measurement of maximum and mean
• Diastolic dysfunction (filling pressure,
velocity gradient across the aortic valve
indirect sign of severity, correlation
(CW Doppler)
with symptoms (PW Doppler)
• Measurment of LVOT velocity (PW
• Elevated pulmonary pressure is a sign
Doppler)
of left heart failure (CW Doppler)
QUANTIFICATION OF AORTIC STENOSIS
Methods
220 mmHg
120 mmHg
Planimetry (TTE) is usually
not possible because the
valves in AS are too
• Planimetry (TEE)
• Pressure gradients
heavily calcified (tracing
! 100 mmHg
• Aortic valve area using
Stenosis results in a pressure gradient.
The pressure gradient is high before the
obstruction and low behind the stenosis.
continuity equation
Evaluation of Gradients
time
the aortic valve orifice
will be difficult).
A late peak of the
Doppler signal
indicates severe aortic
• Gradient = 4 x Vmax
2
stenosis.
velocity (m/s)
(simplified Bernoulli equation)
• Gradients are influenced by
heart rate and stroke volume
• Jet velocity is elevated (> 2m/s)
when AVA < 2 – 2.5 cm2
peak velocity
AORTIC STENOSIS SPECTRUM
– apical five-chamber view/CW
Doppler
LVOT
velocity
AV
trace
Severe aortic stenosis with a peak
velocity > 5.9 m/s during systole.
The baseline is shifted upward
and the velocity range adapted
(8 m/s). Additionally, the LVOT
velocity can be seen within the
AS spectrum, indicating good
Doppler alignment.
Peak velocity
85
009 // AORTIC STENOSIS
NOTES
Patients with bicuspid stenosis
QUANTIFICATION OF AORTIC STENOSIS
Practical Considerations
and those with severe AS
generally have eccentric AS jets.
In these patients you will usually
obtain the highest gradient from
a right parasternal approach.
• Try to be parallel to the stenotic jet and • Use the pencil probe.
optimize the angle.
• In the setting of atrial fibrillation,
• Evaluate gradients from multiple
average the gradients of several beats
windows (apical, suprasternal and right
and the PW-LVOT velocity.
parasternal).
High cardiac output (young or
anxious patients, hyperthyroi-
• Set the focus point of the CW Doppler
in the aortic valve.
dism, fever, dialysis shunts, etc.)
may cause flow velocities >2 m/s
and thus mimic AS.
RIGHT PARASTERNAL SPECTRUM
– right parasternal view/CW
Doppler CW
Doppler spectrum of severe
aortic stenosis from a right
parasternal view. The spectrum is
directed towards the transducer
and is therefore positive.
Measurement of LVOT width
Calculation of Aortic Valve Area (Continuity Equation)
is most critical for
the calculation of the
aortic valve area. Small
LVOT width is measured in the PLAX, slightly proximal to the aortic valve, exactly
where you should also place the PW Doppler sample (5-chamber view).
measurement errors result in
large differences.
A2 x V2
LV
Ao
A1 x V1
LA
A2 = V1 x A1 /V2
LVOT diam = A1
LV=Tvel = V1
AVvel = V2
86
009 // AORTIC STENOSIS
QUANTIFICATION OF AORTIC STENOSIS
NOTES
Limitations of Continuity Equation
To find the optimal location
of the PW Doppler sample
• Measurement of LV may be difficult.
• PW sample volume position plays an
• The true geometry of LVOT (round,
oval) is not appreciated by
• Underestimation of AV peak velocity in
the measurement of distances
volume, place it first in the
AS jet and slowly move the
important role
suboptimal Doppler alignment
sample volume proximally
until there is a sudden
velocity drop.
LVOT DIAMETER – PLAX/2D
The LVOT diameter is measured
on a parasternal long-axis view,
closely below the aortic valve. It
is advisable to slightly overmeasure the LVOT diameter and
thus compensate the oval shape
of the LVOT.
IVS
Aorta
AV
LVOT
diameter
AMVL
Reference Values for Aortic Stenosis
Mean gradient
Aortic valve area
Jet velocity
Mild
Moderate
Severe
< 25 mmHg
25 – 40 mmHg
> 40 mmHg
> 1.5 cm2
1.0–1.5 cm2
< 1.0 cm2
< 3 m/s
3–4 m/s
> 4 m/s
ESC 2012
Valvulo-Arterial Impedance
Valvuloarterial
impedance <3.5
Zva = (SAP + MG)/SVI
• Z(va) = measure of global LV load
• SAP = systolic arterial pressure
increases the mortality
• MG = mean transvalvular
risk 2.3 to 3 fold.
pressure gradient
• SVI = stroke volume index.
87
009 // AORTIC STENOSIS
NOTES
To differentiate between
SPECIAL CIRCUMSTANCES
Low Gradient Aortic Stenosis
true severe and pseudosevere AS, you should
perform a dobutamine
stress echo.
• Mean gradient
< 30 mmHg – 40mmHg
Features of AS
+
red. LVF
• EF < 40%
• AVA < 1.0 cm2
Gradient < 30–40 mmHg
Pseudo-severe AS
Correct classification makes
a difference. Patients with
Gradient > 40 mmHg
True severe AS
Severe AS
Factors in Favor of True Severe
”Low-Flow Low-Gradient” Aortic Stenosis
true aortic stenosis are
potential candidates for valve
• Heavily calcified valve
• LVH (in the absence of hypertension)
replacement.
• Late peak of AS signal
• Previous exams with higher gradients
Patients with paradoxical
low-flow low-gradient AS
”Paradoxical” Low-Flow Low-Gradient Aortic Stenosis
tend to have a higher level of
LV global afterload, which is
reflected by a higher valvulo-
Patients with aortic stenosis and very small ventricles/cardiac output may also have
low gradients in the setting of severe aortic stenosis.
arterial impedance.
Low gradients in severe AS/
normal EF
Low stroke volume (<35ml/m2)
• AVA < 1.0 cm2
• Small, restrictive LV
• EF > 50 %
• Calcified valve
• Mean gradient < 40mmHg
• (Hypertension)
• Concentric LVH ?
The gradients
overestimate AS severity
Aortic Stenosis and Aortic Regurgitation
only when aortic
regurgitation is moderate
• Tend to occur simultaneously
or in excess of moderate.
• Common in bicuspid valves
• Significant aortic regurgitation leads to higher
gradients (overestimation of the severity of aortic stenosis)
88
009 // AORTIC STENOSIS
SPECIAL CIRCUMSTANCES
NOTES
Pressure Recovery
Pressure recovery
may lead to
Increase of pressure downstream from the stenosis caused by reconversion of
overestimation of
kinetic energy to potential energy
gradients.
Where is it relevant?
• High flow rate
• Small aorta < 30mm
• Bileaflet prosthesis
• Moderate aortic stenosis
• Funnular obstruction
SUB- AND SUPRAVALVULAR AORTIC STENOSIS
Subvalvular Aortic Stenosis (Membranous)
• 2nd most common LV outflow obstruction
• Variable morphology (i.e. muscular ridge)
• A transesophageal study is often required
SUBVALVULAR AORTIC
STENOSIS – PLAX/2D
AV
Subvalvular
Membrane
A muscular ridge with a membrane causing obstruction is seen
in the LVOT. In some patients
you will need to scan through
the entire LVOT to detect the
membrane.
AMVL
Other Findings in Subvalvular Aortic Stenosis
Subvalvular obstruction
leads to aortic valve
• Abnormal mitral valve chords
destruction (jet lesion)
• Associated defects (50%) (e.g. PDA, VSD, bicuspid AV, pulmonic stenosis)
and aortic regurgitation.
Echo Features
• Color flow aliasing at the site of
obstruction
• Elevated CW velocity despite normal
AV morphology
• Membrane of varying thickness within
the LVOT, often with a small muscular
ridge. Best visualized on atypical PLAX
views
89
009 // AORTIC STENOSIS
NOTES
Use other imaging modalities
SUB- AND SUPRAVALVULAR AORTIC STENOSIS
Types of Supravalvular Aortic Stenosis
(CT/MRI) and look for other
congenital abnormalities
(Williams syndrome).
Hourglass type
(most common)
Membranous type
Tubular type
INDICATIONS FOR AORTIC STENOSIS
SURGERY/INTERVENTION
When the patient does not
Indications for Surgery in Severe AS (Class I/ESC 2012)
fulfill the criteria/indications for
surgery, annual follow-up
should be performed. Shorter
intervals are necessary when AS
is severe, heavily calcified or
when symptoms are uncertain.
• Symptomatic patients with severe AS
(dyspnea, syncope, angina)
• Symptomatic patients with severe AS
• When other cardiac surgery
is being performed (e.g. CABG;
ascending aorta)
and reduced LV function (<50% EF)
• Asymptomatic patients with severe AS
and abnormal exercise test
The indication for aortic
Other Things to Consider in Asymptomatic Severe AS
valve surgery must be
established individually.
Consider age, comorbidities, the risk of
myocardial fibrosis in
LVH, longitudinal
dysfunction, the degree
of calcification, the
patient‘s preference and
expectations, the rate of
progression, etc.
90
• Valve morphology (bicuspid)
• Severity of AS (very severe AS)
• Degree of calcification
• Subclinical myocardial dysfunction (longitudinal function)
• Rapid progression
009 // AORTIC STENOSIS
INDICATIONS FOR AORTIC
STENOSIS SURGERY/INTERVENTION
NOTES
Transcatheter Aortic Valve Replacement (TAVR)
The indications for TAVR may
change with improvements in
methodology.
Consider interventional valve replacement in:
• Symptomatic/severe aortic stenosis
• High-risk patients
• Suitable anatomy (AV annulus diameter)
• Appropriate anatomical access for valve implantation (transfemoral/transapical)
TRANSCATHETER AORTIC VALVE
– PLAX/2D
The steel frame and the bovine
pericardial tissue leaflets of an
Edwards-Sapien valve are visible
in the aortic annulus.
Steel Frame
Bovine Valve
Echo Assessment for TAVR
Consider alternatives for the
measurment of the aortic
• Establish the presence of
severe aortic stenosi.
• Assess annular dimension during
systole in a zoomed PLAX for valve
sizing Undersizing may lead to device
migration or significant paravalvular
• Assess the extent and
distribution of calcification
• Exclude patients with bicuspid valves
(an ellipitical orifice may predispose to
valve annulus (2D/3D TEE,
CT), as these methods are
more accurate than 2D
echocardiography.
incomplete valve deployment)
• Exclude patients with basal septal
aortic regurgitation. Oversizing increases
hypertrophy and dynamic LVOT
the risk of underexpansion, reduces
obstruction
durability, and increases vascular
access complications
91
009 // AORTIC STENOSIS
NOTES
92